Background Art In prior art chairs to be assembled in two frames for instance (front legs frame and rear legs frame which extends upwards with the back, otherwise laterally opposite frames) jointable in a detachable way are known.

The jointing systems are various using squares or dowels shrouded in the wooden uprights or cross-pieces and tie screw means for the clamping.

Drawbacks The present solutions are complex, expensive and are characterised by a limited strength so that often a loosening or breakage danger in the jointing areas occurs.

Purpose of the invention The purpose of this invention is that of obviating the above mentioned drawbacks.

Essence of the invention The problem is solved as claimed by a chair to be assembled in two opposite frames jointable in a detachable way, characterised in that: -each of said two opposite frames has, at least one middle strong cross- piece at the seating height in which at least two spaced transversal notches having dimensions suitable to housing a metal plate with a threaded hole, being said cross-pieces internally transversally holed in correspondence of said plate hole axis, are obtained;

-a bearing seating frame supplied with at least two opposite sides with transversal holes coinciding with the previous ones is provided and; -at least four threaded screws for clamping, in said coinciding holes, said opposite frames with said bearing seating, by the screwing from the inside on said metal plates of said screws are provided.

Thus a chair completely detachable and stackable in a flat package with minimum bulk is obtained.

Advantageously the opposite frames consist of one frame making up the front legs and one frame making up the rear legs with an extension towards the back's top.

As much advantageously said frame seating is an under-frame seating to which an interchangeable seating is fixed.

In alternative said frame seating is integrated with the seating.

Advantageously said frame seating has a system for fixing to said opposite frames by means of four pins or tongues which fix into the respective uprights of said opposite frames.

Thus a stronger and safer fixing against the danger of the four screws loosening is obtained.

As much advantageously said screws are opposite threading screws and while on a side they lock-screw with said plates up to the threading end, substantially for the plates thickness, on the other they house in engagement a nut with eventual washer for completing the clamping.

Thus the danger in the bolt use, of clamping by screwing beyond the plate thickness with the risk of breaking the cross-piece for the screw protruding beyond the plate thickness is avoided.

Description of at least one form of invention embodiment These and other advantages will appear from the followillg description of a preferred solution of embodiment, with the aid of the

enclosed drawings, whose details are not to be considered as limiting but only as examples.

Figure 1 is a view. of the assembled chair in cross section to the seating height, showing the assembling system.

Figure 2 is an enlarged view in cross section on the vertical plane showing the clamping system by tie-screw with the metal plate.

Figure 3 is a perspective view of metal plate, washer, tie-screw and clamping nut.

As it can be seen from the above shown figures, with 1 and 2 the opposite frames to be assembled are indicated.

Each frame has a cross-piece 12,22 at the seating height which is fixed by tonguing or lock-pins to the respective uprights which make up the rear legs and eventual back extension for the rear frame and only legs for the front frame (11,21).

The frame seating 3 has a quadrangular shape with four sides (31,32) locked to one another by a pin and stiffened by a central cross-piece (33) eventually holed (330) for the upper fixing of the interchangeable seating (not shown).

Obviously the seating might also be integrated with this frame.

This frame has four lock-pins on the corners (L) for the fixing with the opposite frames (1,2).

The cross-pieces of the opposite frames (12,22) have some notches (120) for housing a metal plate with threaded hole (4) and the assembling and fixing occurs by four tie-screws as claimed.

As it may be noticed from figure 3 said screw is substantially a stud- bolt having a threading depth equal to the thickness of the plate (4) so to be locked into it.

The clamping completion will be carried out from the inside by means of

nut and washer (6,6').

Thus the clamping can be carried out as much as necessary with no danger of breaking. the cross-piece because the screw will never exit from the plate's other side.